The field of aeronautical telecommunications has undergone substantial development in the last few years.
Conventional avionics networks use a bus topology to which are connected pieces of avionics equipment. These networks comply with standard ARINC 429.
The more recent avionics networks are generally of the AFDX® (Avionics Full Duplex Switched Ethernet) type. The AFDX® network was specifically developed for the constraints of aeronautics and is based on the principle of switched Ethernet. Recall that switched Ethernet networks can operate under two separate modes but compatible between them: a shared mode, wherein the same physical support is shared between the terminals, with random access and detection of collisions between frames, and a switched mode, wherein the terminals exchange frames by virtual connections also called virtual links, which guarantees the absence of collisions.
The AFDX® network underwent a standardisation in standard ARINC 664, part 7. There is in particular a description of the AFDX® network in the document entitled “AFDX protocol tutorial” available at URL http://sierrasales.com/pdfs/AFDXTutorial.pdf as well as a presentation of the virtual links in FR-A-2832011 filed in the name of this applicant. Simply recall here that the AFDX® network is full-duplex, deterministic and redundant.
Full-duplex means that each subscriber to the network (terminal, calculator) can simultaneously send and receive frames over the network. The AFDX® network is also deterministic, in that it implements virtual links that have guaranteed characteristics in terms of latency limits, physical flow segregation, bandwidth and flowrate. To do this, each virtual link has a path reserved from end to end through the network. Finally the AFDX® network is redundant because the underlying Ethernet network is duplicated for reasons of availability.
A piece of equipment subscribed to an AFDX® network is directly connected to a switch of this network. The data of a subscriber is sent in the form of IP packets encapsulated in Ethernet frames. Contrary to conventional Ethernet switching (that uses the Ethernet address of the recipient), the switching of frames on an AFDX® network uses a virtual link identifier included in the frame header. When a switch receives a frame on one of its input ports, it reads the virtual link identifier and determines using its switching table the output port or ports whereon it has to be sent.
A source piece of equipment subscribed to the AFDX® network can send AFDX® frames to one or several pieces of recipient equipment subscribed to the same network, using a virtual link (unicast in the first case and multicast in the second case).